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Safe sun exposure is essential for optimal health, but incorrect exposure can raise your risk of skin cancer while not providing any health benefits. Sunburn should be avoided at all cost. Detailed guidelines are provided for safely increasing your vitamin D stores through proper sun exposure are included

While sunlight is composed of about 1,500 wavelengths, UVB is the only wavelength that will produce vitamin D when hitting unexposed skin. UVA’s increase your risk of skin cancer and causes photoaging of your skin. Therefore, it’s important to determine the ideal times of year for safe and effective sun exposure, and avoid exposure during times that UVB rays are not present. Instructions are included

Vitamin D3 is an oil soluble steroid hormone that forms when your skin is exposed to UVB radiation from the sun (or a safe tanning bed). When UVB strikes the surface of your skin, your skin converts a cholesterol derivative into vitamin D3. It takes up to 48 hours for this vitamin D3 to be absorbed into your bloodstream to elevate your vitamin D levels.

In case you do develop a sun burn, immediately apply raw aloe vera. It’s one of the best remedies to help accelerate skin healing

Little Sunshine Mistakes that Can Give You Cancer Instead of Vitamin D

March 26, 2012|802,208views

Unfortunately, due to decades of professional and media misinformation, the typical American believes they should avoid the midday sun and need to use sunscreen before, and several times during, sun exposure.

Unfortunately, this is a prescription for minimizing vitamin D levels and all its widely appreciated benefits.

The purpose of this article is to provide you with some practical guidelines on how to use natural sun exposure to optimize your vitamin D benefits.

Your Initial Exposure

The first few days, you should limit your exposure to the sun to allow your body's melanocyte cells to rev up the ability to produce protective pigmentation that not only gives you a tan, but also serves to help protect you against overexposure to the sun.

If you are a fairly light skinned individual that tends to burn, you will want to limit your initial exposure to a few minutes, especially if it is in the middle of summer.

The more tanned your skin will get, and/or the more tanned you want to become, the longer you can stay in the sun. If it is early or late in the season and/or you are a dark skinned individual, you could likely safely have 30 minutes on your initial exposure. If you are deeply pigmented and your immediate ancestors are from Africa, India or the Middle East, it is possible you may not even have to worry about the timing of your exposure.

Always err on the side of caution however, and let it be your primary goal to never get sun burned.

You can use a moisturizing, safe, NON-SPF cream to moisturize your skin, or use something as simple as organic coconut oil to moisturize your skin as this will also benefit you metabolically. Remember if the moisturizer you use has an SPF value, it will block UVB rays and will not allow your body to produce any vitamin D. The rest of the day, you can spend in the shade, wear clothes, and, if you still want to be in the open sun, use a non-toxic lotion with SPF15 for uncovered skin. Just be sure to be on the safe side of burning!

Protect Your Face and Eyes

The skin around your eyes and your face is typically much thinner than other areas on your body and is a relatively small surface area so will not contribute much to vitamin D production. It is strongly recommended to protect this fragile area of your body as is at a much higher risk for cosmetic photo damage and premature wrinkling. You can use a safe sun block in this area or wear a cap that always keeps your eyes in the shade like I do when I am outside seeking to increase my vitamin D levels.

Prepare Your Skin and Keep Your Vitamin-D Supply Constant

Before you travel, prepare your skin by having sessions (1-2 times per week) in a solarium with low-pressure UV-lamps that has a reasonable percentage UVB. This will also protect you against vitamin D deficit between your vacations. The time for each session depends on how strong the tubes in the solarium are. In countries that follow the EU-norm you probably will need 15-20 minutes, while in less regulated countries, 5-10 minutes might be enough. The operator of the tanning place should be able to advice you.

How Do You Know if You Are Getting Enough Vitamin D?

The key point to understand is that sunlight is composed of about 1500 wavelengths, but the only wavelength that will have your body make vitamin D are UVB-rays when they shine on unexposed skin. The key is that the UVB-rays from the sun actually have to pass through the atmosphere and reach where you are on the earth. This obviously does not occur in the winter for most of us, but the sun's rays are also impeded during a fair amount of the year for people living in temperate climates.

So how do you know if you have entered into the summer season and into the time of year, for your location, where enough UVB is actually able to penetrate the atmosphere to allow for vitamin D production in your skin?

It should be noted that this represents a very small portion of the total radiation from the sun that reaches the earth's surface. Much is filtered out by our atmosphere. So due to the physics and wavelength of UVB rays it will only penetrate the atmosphere when the sun is above an angle of about 50° from the horizon. When the sun is lower than 50°, the ozone layer reflects the UVB-rays but let through the longer UVA-rays.

The first step is to determine the latitude and longitude of your location. You can easily do this on Google Earth, or if you are in the U.S. you can use the TravelMath Latitude Longitude Calculator to find your latitude and longitude i. Once you have obtained that you can go to the U.S. Navy site to calculate a table to determine the times and days of the year that the sun is above 50 degrees from the horizon ii. Please view the video at the top of this page. The URL for the US Naval Observatory Azimuth table is http://aa.usno.navy.mil/data/docs/AltAz.php

For a more detailed understanding of this you can visit the University of Colorado State's page iii that discusses this in more detail. If you read the paper you will see that there are other factors, such as ozone concentration, altitude, air pollution, ground covered by snow or ice, and cloud cover that also contribute to the amount of UVB that is ultimately reaching your skin.

Translated to the date and time of some places on the globe, it means for example: In my hometown of Chicago, the UVB rays are not potentially present until March 25, and by September 16th it is not possible to produce any vitamin D from the sun in Chicago. Please understand it is only theoretically possible to get UVB rays during those times. If it happens to be cloudy or raining, the clouds will also block the UVB rays.

This is one of the reasons I now spend most of my winters in the sunshine state of Florida because in the center of the state there are more than two extra months of UVB as the sun doesn't disappear for winter until October 23 and comes back again much earlier, around February.

When NOT to Tan

From a health perspective it doesn't make much sense to expose your skin to the sun when it is lower than 50 degrees above the horizon because you will not receive any valuable UVB rays, but you will expose yourself to the more dangerous and potentially deadly UVA rays. UVA's have a longer wavelength than UVB and can more easily penetrate the ozone layer and other obstacles (like clouds and pollution) on their way from the sun to the earth. UVA is what radically increases your risk of skin cancer and photoaging of your skin. So while it will give you a tan, unless the companion UVB rays are available you're likely doing more harm than good and should probably stay out of the sun to protect your skin.

During the times of the year when UVB rays are not present where you live you essentially have two options: You can use a safe tanning bed or you can swallow oral vitamin D3.

Avoid Tanning through a Window as it Will Increase Your Skin Cancer Risk

Because the UVA has a longer wavelength, it penetrates materials more easily, such as the earth's atmosphere and window glass which will effectively filter out the majority of UVB radiation, but only minimally filters out UVAs. What's the significance of that, you ask?

It's important to remember that vitamin D3 is formed from exposure to UVB rays, whereas UVA radiation actually destroys vitamin D. This helps keep your body in balance; it's one of the protective mechanisms your body has to avoid overdosing on vitamin D when you're outside. However, when you're exposed to sunlight through windows -- in your office, your home or your car -- you get the UVA but virtually none of the beneficial UVB.

This can lead to significant health problems, because in addition to destroying vitamin D3, UVA's also increase oxidative stress. UVA is one of the primary culprits behind skin cancer, and it increases photo aging of your skin. It's also what causes you to tan. You can actually get vitamin D without significantly darkening your skin, because the UVB wavelength does not stimulate the melanin pigment to produce a tan.

Normally, of course, when you get tanned from outdoor sun exposure you're getting both UVA and UVB at the same time, so it's not a problem. But when you are indoors and expose yourself to sunlight filtered through window glass, you are increasing your risk of a variety of conditions, primarily skin cancer, because the UVA's are effectively destroying your vitamin D3 levels while you're getting none of the benefits from UVB, and this can significantly increase your risk of skin cancer. This is one of the reasons why many that drive long hours in their cars develop skin cancer on the arm next to the car window.

The Antioxidant that Reverses Skin Aging from the Inside Out

An excellent adjunct to vitamin D is the antioxidant astaxanthin. Not only can it act as an internal sunscreen, protecting your skin from harmful radiation—both solar and medical radiation—but it also appears to have a rejuvenating effect on skin in general. Two human clinical studiesiv were recently performed to test the effects of astaxanthin on skin aging. In the first, 30 healthy female subjects were given six mg per day of oral astaxanthin plus two ml per day topical astaxanthin application, for eight weeks. The women showed improvement in:

Skin wrinkle size

Age spot size

Elasticity

Skin texture, and

Corneocyte layer moisture content

The second study was a similar test on 36 healthy male subjects for 6 weeks. The men showed improvement in crow's feet wrinkle size and elasticity, transepidermal water loss, moisture content and sebum oil level. According to the authors:

“These results suggest that astaxanthin derived from Haematococcus pluvialis may improve the skin condition in not only in women but also in men.”

What to Do if You Get Sunburned

If you ever develop a sunburn it is important to realize that aloe vera is one of the best remedies to help repair your skin as it is loaded with powerful glyconutrients that accelerate healing. Ideally, it is best to use the gel from a fresh plant, but there are commercial products available that have active aloe in them. Ideally you would never need it because you are using these safe tanning guidelines, but accidents do happen and it is important to have contingency plans for them.

Testing Your Blood is the Only Way to Know Your Vitamin D Levels

The above guidelines are the most comprehensive details that I know of that will allow you to optimize your vitamin D levels by natural sun exposure. However, there are other variables that you can't control, such as the darkness of your skin and your age, which can add further confusion to the ability to accurately predict what your vitamin D level will be after appropriate sun exposure.

I can tell you that these guidelines work and have personally used them to maximize my vitamin D levels. I have not taken any oral vitamin D for years now. Last spring, with one to two hours of sun exposure regularly, I was able to get my vitamin D level to 105, which is typical of lifeguards that are not using sun screens.

I would strongly encourage you to have your blood level checked to confirm that your sun exposure is putting you in the right level. If it isn't, or if sun exposure is not a practical option for you, then you should consider supplementing with oral vitamin D3. (You want to avoid vitamin D2 as it is clearly inferior to D3.) The following chart shows the therapeutic levels of vitamin D you'll want to reach and maintain.

A word of caution about sunscreen products. The latest science shows that Titanium Dioxide nano-particles used in sunscreen have been shown to cause brain damage in fish and mice. These nano-particles can be absorbed through your skin and circulate in your body. Titanium and Aluminum are both capable of passing the blood brain barrier and like other metals and metalloids can develop beta-amyloid brain plaques the classic abnormality in Alzheimer's disease.

ScienceDaily (Sep. 18, 2011) — "Scientists at the University of Plymouth have shown, for the first time in an animal, that nanoparticles have a detrimental effect on the brain and other parts of the central nervous system."

Titanium dioxide creates free radicals in photocatalytic reactions with UV light and your skin can be damaged by these free radicals. To reduce this effect manufacturers coat Titanium dioxide with Aluminum oxide and or Silica. However, this makes the product worse because Aluminum is electropositive and readily reactive, easily absorbed by the body and also capable of forming beta-amyloid plaques.

Both Aluminum oxide and Titanium dioxide can lead to Alzheimer's disease because like other metals and metalloids they are capable of passing through the blood brain barrier forming beta-amyloid plaques. These materials should never have found their way into any consumer product that is put on the skin, could be inhaled or ingested. On a positive note: Vitamin E reverses the effect of dietary aluminum on lipid peroxidation, amyloid ß peptide formation, and plaque deposition.

The EWG list of sun screens was published before real scientific studies revealed that Titanium Dioxide is damaging to the nervous systems of animals. You cannot trust manufacturers bringing products to market

I am really glad I never used any of those kind of things. I remembering asking my mother why we didn't use sun screen after watching my aunt cream up my cousin before we went into the swimming pool. And she told me because we didn't want to plug up the filter. Sure enough there was an oil float all over the pool, it took an entire night of non-use before we got the oil slick cleaned up. And as we each got out of the water it coated everyone who hadn't had it spread all over them. I felt like I needed a shower instead of feeling refreshed like usual.

It would be interesting to know the body burdens of metals in the public. Aluminum is considered "safe" and whatever is smoked or slathered on skin is ignored (not regulated or considered). Vitamin E protects fats from oxidation and like other antioxidants is recharged with available electrons donated by Vit C...or generated in mitochondria...or gathered from the Earth...or even taken directly from sunlight in processes unknown. Sunbathing should be accompanied by all antioxidant electron sources possible and exposure built over time.

Samsel, thanks once again for giving us the benefit of your expertise. You are one of the members that truly make this website worthwhile. I've always felt the chemicals in sunscreen products are probably as bad as the lack of sun itself. I never use the stuff.

Dr. Mercola's brand of sunscreen does contain Titanium Dioxide. It also contains zinc oxide. I have a bottle here..should I be concerned? I don't use it often, just if I need to be out without a hat or for longer periods in the sun. I've had it for a couple of years and I see it expires this month of this year.

To get natural sun protection from both UVA and UVB rays, you will want to use a sunscreen product that contains the active ingredients of titanium dioxide and zinc oxide. You want to be cautious not to include any vitamin A in your sunscreen, or its derivatives retinol and retinyl palmitate. Other safe ingredients that will nourish your skin include Coconut oil, Jojoba oil, Sunflower oil, Shea butter, Vitamins D and E, and Eucalyptus oil.

Thanks to the Environmental Working Group, you are now able to see exactly how your sunscreen rates for safe ingredients and efficacy. Check out EWG's Sunscreen Guide here. www.ewg.org/.../best-beach-sport-sunscreens Their website also lists the titanium and zinc containing sunscreens receiving the highest ratings, as well as provides you with some non-mineral options that rank lowest on the toxicity scale.

@ArizonaSharona: The EWG's list of sun screen products was published before scientific studies revealed that Titanium Dioxide is damaging to the brains and nervous systems of animals. You cannot trust manufacturers bringing products to market, many things the Government labels 'generally recognized as safe' GRAS are not. I would err on the side of caution with any product you put on your skin. Absorption is just one of the three routes of poisoning.

"Both nano-size zinc oxide and titanium dioxide, including forms extracted from sunscreen, react strongly with UV light (Dunford 1997) and may damage skin cells (Sharma 2009)" EWG. It should be noted that particles do not need to be nano for absorption remember that your Biome contains billion of bacteria both internally and externally on your skin that are capable of assimilation and transfer becoming part of you !

@ForbiddenHealing: Aluminum is not safe and smoking anything is not safe either. I remember a couple of years ago you mentioned about smoking and reversing the effects with vitamin C Bicarbonate. Remember Vitamin C Bicarbonate is produced today from genetically engineered corn most likely carrying micro RNA contaminates with it. Tobacco is a no no period end of statement, so if you are still smoking give it up immediately. Tobacco is now genetically engineered and has been for some time.

@Lovemywesties: Thank you for your comments, your participation in the Mercola community is appreciated.

Seems that some do not appreciate the comments about Titanium Dioxide and keep removing points from the thread to drive it out of sight. This posted thread was at the top and continues to go up and down like a yo-yo ! I can't believe that the four points each given to Reverend Alan, Lovemywesties et al got taken away, very strange.

@ Samsel, your scrutiny about the EWG's reasearch being out dated deserves some merit. For me, when I am done with my preferred sun exposure i cover up with clothing and a large brimmed hat. It is important to note that continued sun exposure after your body produces vitamin D will aid in the destruction of vitamin D. In studies Vitamin D can be destroyed by over-treatment with ultraviolet (UV) light and by peroxidation in the presence of rancidifying polyunsaturated fatty acids. That being siad, perhaps the use of oils that go rancid in with sun exposure and heat may also add to the destruction of D while you spend the rest of the day in the sun covered in sunblock. That is if the oils in the block are polyunsaturated.

@extremehands1: Thank you for your comment. I sent an email earlier today to Ken at the Environmental Working Group suggesting that they revamp their sunscreen list to reflect the latest science. I do not know when I will hear back but I will let the community know. Although retired, I am still working on environmental cases in the USA affecting thousands of people free of charge. As an expert in the field of hazardous chemical and biological materials I continuously update my knowledge base with the latest studies. The science and understanding of hazardous materials is changing rapidly with specialized studies and greater communication among scientists of many disciplines.

@Samsel: you are indeed a valued member of this community; it's clear you have a high degree of expertise and I take your comments very seriously. BTW, I think ForbiddenHealing was speaking tongue-in-cheek with his comments about aluminum and smoking, i.e. conventional wisdom does not consider aluminum hazardous — after all, it's found in everything from cookware to antiperspirants (oh yeah, and in the brain tissue of Alzheimer's victims).

Never used sunscreen myself...which is why one side of my face is wrinkled from 12 years of facing the same way in the greenhouse! Of course, I didn't know then what I know now. :-(

Thanks for valuable info as usual samsel. There is science to back you up on the caution about putting anything on your skin. A Swedish study (sorry, I can't find the ref. right now) found that just putting the oils making up the basic components of "skin care" products on your skin affects the genetic expression of the cells, and many "moisturing" products actually decreases the moisture holding capacity of the skin.

About nano particles, even the pro-nano particle people say that far too little is done regarding the research of safety for these new materials. The tech guys come up with new ideas to sell "better" products in a pace that is impossible to keep track of, even for a watchful expert like samsel. And only about 1 % of allthe money spent on research in this field has anything with health to do. It's much like the hype in the GM business field.

Reverend Alan, that story reminds me of a surfboard used as a sign on the beach at a marine reserve in Maui, urging snorklers to not use any sun screen products, since it will poison the marine life. That's as good a reason as any to avoid such products, don't you think?

@Mercola.com Tony R -- look what i just found on "House Calls" website. I wonder if someone has any info on it. "If the form of vitamin A used in yours is retinol, you’re golden -- because a new study finds that people who get this form of A have a 60 percent lower risk of melanoma. And those who got the most A of all -- 1,200 mcg a day -- were 74 percent less likely to suffer melanoma, according to the study in the Journal of Investigative Dermatology.

The "catch" here is that vitamin A from food -- like liver (calf or chicken), kale, spinach or carrots -- didn’t make a bit of difference. The vitamin A precursors such as beta-carotene and lycopene used in many multivitamins didn’t make the cut either." Altho it may well be a "study" financed by some large supplement manufacturer, it may well be worth looking into it.

@Vikingstork: The benefits of Vitamin D cannot be understated, but the increasing lack of adequate levels of this vitamin in the general population is disturbing. Sunshine and a mineral rich diet containing Zinc are important factors for maintaining adequate levels of vitamin D.

In 2008 the Copenhagen Consensus noted a simple solution to the fifth leading risk factor for disease in the world, Zinc deficiency, could be solved by providing micronutrients containing zinc, to humans. Zinc deficiency may be a leading cause of Vitamin D deficiency. Both Vitamins A & D are necessary for Zinc absorption. In 2008 an interesting study demonstrated reproducible results to increase Zinc levels. "Plasma zinc levels increased significantly (p < 0.02) from 11.82 (+/-2.60) to 13.32 (+/-3.04) mum/L only in the group receiving the combination of zinc and vitamins A and D. This novel method of increasing plasma zinc levels by the augmentation of vitamins A and D may have implications for the reduction of burden of disease." www.ncbi.nlm.nih.gov/.../17171460

There is an undeniable relationship between Zinc and vitamins A & D, but the question remains what other causes may be creating Zinc deficiencies in the body? The first two and probably the obvious causes of malabsorption are replacement of Zinc by metalloids, metals like Cadmium and food lacking in Zinc like Genetically Engineered Food.

Arsenic, Cadmium and other more reactive metal and metalloid exposure from the burning of Fossil Fuels, particularly COAL will replaces Zinc in the body. By replacing zinc, these metals and metalloids interfere with the production and absorption of vitamin D. Genetically modified food can also be another reason for the lack of Zinc. Genetic modification of food crops has been shown to interfere with the uptake of Zinc and chelates nutrients in the plants, making them less available. These deficient crops are not an adequate source of Zinc and are a large portion of peoples diets.

The presence or absence of nanoparticles in sunscreen is a concern, but there are none in Dr. Mercola's sunscreen products. I understand from that, that the titanium dioxide and zinc oxide are not absorbed through the skin. See his product page here: products.mercola.com/summer-survival-kit

The more I read about vitamin d the more complicated it gets. Think I'll just keep on doing what I have been doing, getting tanned, & trying not to get burned by the sun. I listen to my body. When i lay out on my back deck, I can feel when I have had enough. I do take a suppliment during the winter months, as my d leval is low during that time. However, I think this is because my ldl cholesterol is low. I might add showering once a week may be fine for some people, but I prefer to shower every day. Yes I do use soap on underarms etc. I do not like smelling like a wild animal, & am certainly glad my lady doesn't. Good health to all.

This kind of anxiety about how you smell is so "teen", and manufactured by those same people you are donating your money to for worse than useless products. How are they going to keep the lie alive unless they put a doubt in your mind about your social acceptability? Fact is you will be sweeter without soap because soap causes an imbalance of skin microorganisms, and unhealthy skin in general, and that stinks! Wash your butthole with a spray of warm water after you sh*t, and every couple days shower with warm water, and you're good to go. Unless you're a coalminer! Nature usually gets things right, you know!

Excellent, Moonwest. Actually wild animals rarely have an odor; only animals kept in confinement do. Also, like most in the U.S., I was taught to wipe with paper after using the toilet. It wasn't until I traveled abroad that I discovered how much cleaner other cultures are — instead of smearing with paper, they clean with water. I've also discovered that on a healthful diet, there's little or nothing to clean anyway.

Of course one needs to soap up every morning! But does one really ever need soap on the broad expanses - back, legs, arms, stomach - where most of the sun exposure occurs? If you're only using warm water on those parts, do you have to worry about the 48-hour rule? And Just how much vitamin D is absorbed in 24 hours - do you really absorb that much more in the following 24? If you're out in the sun every day, what difference does it make if you shower every 24 hours?

Wow!! I sat out in the garden on a beautiful day today here in London (UK)and thought as long as I didn't bathe before midday or after 2pm I'd get the max possible exposure to UVBs. It turns out I was 3 weeks premature. The angle of the sun here won't hit 50 degrees till April 20th-and then only for half an hour. What's more it will only last till 22nd August, after which no more Vit B production will be possible here till the following April. What an amazingly small window and to think we still call August our summer. In fact our kids are still off on their summer break at that time. Usually they go back the end of the first week of Sept. What a fantastic find Doctor. If you'd asked me I would have said it would be fine to bathe from say mid March till maybe early October. Soooo glad I know better now and that I'll be able to control my exposure to the nearest 10 mins in future. Thankyou. Your site really is the most wonderful resource.

Thanks Dr. Mercola for an excellent article on vitamin D metabolism. You have provided us with a detailed road map to safely maintain adequate levels of this important vitamin.

My interest in vitamin D was tweaked about 10 years ago when I was giving a lecture about CARB syndrome at an ACAM conference in Florida. Carbohydrate Associated Reversible Brain syndrome or CARB syndrome is a new disease model that explains how the combination of excessive fructose primarily from sugar and HFCS and high glycemic carbohydrates is triggering a chronic brain disorder that results in a long list of brain dysfunction symptoms and causes people to store excessive fat at any caloric intake.

I thought my lecture went fairly well and I sat down to listen to the next speaker, Dr. Michael Holick from Boston University. As it turns out, Dr. Holick is the researcher who almost single handedly sparked the public’s interest in vitamin D. I was totally blown away by his talk, which included many of the elements discussed in this article. After his lecture he sat down next to me and we spent the next 30 minutes discussing the details of vitamin D metabolism. He also told me that he had been fired from the Dermatology Department at Boston University for advocating that people spend time in the sun to boost their vitamin D levels!

Since then I have been following many of Dr. Holick’s recommendations, which are essentially identical to those discussed in this article and I have also shared this information with my patients. It’s great to see Dr. Mercola making this valuable information available to a wider audience.

@docww - KK is right about oral D3 and hypercalciuria. Doctors have vilified Vitamin D3 for directly causing hypercalcemia. Calcification of the heart, kidneys, brain raises an alarm, and semi-knowledge is the danger. Those who injest a good amounts of D3 might saturate the whole body within a few months. After that, cessation of D3 makes more sense for the sake of caution.

Vitamin D3 gets down into genetic programming to fight cancer, but prolonged D3 treatment disrupts balances necessary for optimum health. Deficiency of Vitamin K2 is especially dangerous,and further study of disruption of Vitamin A might be encouraged.

I wonder why my animals love to sunbathe in the windows of my house. On nice days both my dogs and cats love to plop themselves down by the window and soak up the warmth. Is this bad for them? Does their fur protect them from the bad rays?

Glass windows have been around for a lot longer than one hundred years. The first glass greenhouse conservatories in England appeared around 1500 AD. Here is some information about glass and windows. Glass making began in ancient Babylon and Mesopotamia around 3000 BC as noted by glass making recipes on cuneiform tablets. My ancestors the ancient Romans were the first to make flat glass for windows which was opaque. The city of Pompei may also have had greenhouses because of building orientation and their knowledge of harnessing the sun's energy. Later in the 'Dark Ages' better techniques and materials made glass clearer. In about the 12th century stained glass was used as both an art form and to allow light into churches and cathedrals.

Todays glass used in buildings is not the same as old glass used in window panes. Low E glass filters and allows visible light to penetrate the living space but reflects longer infrared light waves producing heat back into the space.

@Reverand Alan: My stepfather was German hence the last name, my mother was Italian we share an interesting ancestry !

@utahbelle2011: Different glasses let different parts of the sun's light through. Most likely, almost *no* UVB radiation is coming through the glass. And possibly, the UVA doesn't get thorough, either. (So they're probably not producing any vitamin D!) ;) But regardless, I'd guess their fur definitely would protect them, even if it did come through. In sheep, their fur produces lanolin which turns to D in the UV light, and then they lick it to ingest it. (I believe other furry mammals do similar things?) I think they'll know to move if it's too much! ;)

@Joseph: you seem to be fairly knowledgeable about UV transmission so I'd like to pick your brain. What can you tell me about the transmission of UVA and UVB through the double layer of 6-mil poly in greenhouse construction? (The left side of my face tells me that UVA probably comes through just fine....)

@Islander: It depends on the plastic. Plastic greenhouse sheeting ( 6mil poly ) does not transmit the full spectrum of light. Depending on the plastic formulation and coatings used will provide different light transmission and absorption properties. IR film for greenhouses holds heat in longer similar to low E glass. UV inhibitors are added to greenhouse plastics to prevent degradation and extend the life of plastic sheeting 4 to six years.

Greenhouses sheethed in plastic grow inferior weak plants. Glass houses (old style cypress or redwood bars and 16x24 glass are superior for good strong, turgid plant growth. Old style glass greenhouses are the next best thing to growing outdoors. Having owned and invested in a commercial greenhouse range ( with over fifty-thousand square feet of glass ) employing many people to grow and care for the structure I can attest to the quality of both ornamental and food grown under the 'crystal palace.'

@Samsel & Joseph: I closed my garden center in 2001. It's not for myself that I'm concerned. My best friend will soon be taking delivery of a small greenhouse and asked me about that this very morning. I'm curious, for her sake and mine, in retrospect.

@Islander & @Samsel: There are *so* many kinds of plastic... but most of them actually not only attenuate in the deeper UV, but are actually susceptible to UV photo-degradation. That is, the UV light will break-down the plastic, and make it less clear over time. Most folks think that plants only use light in the Green and Red portions of the spectrum... but as Samsel points out, just like the rest of life on earth, it seems that plants know what to do with the whole spectrum.

"....From a health perspective it doesn't make much sense to expose your skin to the sun when it is lower than 50 degrees above the horizon because you will not receive any valuable UVB rays...." - Can somebody explain to me what is the time of day when we should be avoiding the sun exposure? Thank you!

yes, i'm wondering the same thing about the time of day this would be. Also, what about us girls who shave our legs daily - i use soap to do that! is there something that won't strip the oils that can be used instead? thanks :)

The usual recommendations are between 10 a.m. and 2 p.m., meaning as close to solar noon as possible. But note this: when your shadow is longer than you are tall, the sun is too low and you are getting no UVB — only the harmful UVA. Cover up!

@luktannr...There is a book by Krispin Sullivan called Naked at Noon. She explains alot about sunning. I was ignorant and when I first moved to AZ, I walked in the early morning hours, thinking I was getting Vit D. I guess all I did was damage my skin. As far as shaving your legs, I would suggest just skipping a day or two as I do. You can resort to waxing as that may last longer.

@Handlewithcare: I think the good Dr. should've said "...From a *UVB* perspective..." All he's saying is that UVB (which we need for Vitamin D production) is only available during those times - and that's a valuable commodity. But there's lots of other wavelengths (colors) in the sun that our body (and eyes) need. So, I believe, it's not that the sun is bad... just that when there's not any UVB (at those 'peak times'), there *still* is UVA - which can definitely burn & age your skin if you get too much. Perhaps it's better said that outside of this 'peak window' we should *moderate* our sun exposure, as appropriate for our skin type and location. Does that help?

Here is the site to determine your peak hours for UVB or Azimuth. aa.usno.navy.mil/.../AltAz.php For my area and for the second half of the month, I get UVB from 1 to 1:30 only, adjusted for daylight savings.

Also, lukannr, I shave with a little coconut oil. Works really well, no razor burn even in the bikini area and armpits, and my skin is soft and moisturized afterword. The coconut oil is good to have on your skin when you go out into the sun - has natural sunscreen properties. I tend to think it does not remove my natural body sebum or D to use this. I could be wrong, but my skin certainly is not dry and oil free like when I used to use soap.

I put a teaspoonful or more into a shallow dish or cup. In the winter I just leave it on the spoon because it is solid and melt it on my hands before applying. The water helps it to spread easily. I keep a small container of coconut oil in the bathroom for washing my face every night and just take a teaspoon out of there into the shower. When I get out I put a little baking soda on my armpits and ready to go. My family (who can be mercilessly honest with me) have not said I smell, and people don't back away from me when I visit. Soooo

Just one more way the F.D.A is going to control us! more people get skin cancer on the Canadian border than in the south where people get much more sun Exposer the whole year! Sun tan lotion is loaded with chemicals, that are absorbed into the body "chemicals cause cancer" especially with exposer to the sun! Because heat opens up the pores and allows more absorption! Vitamin 3 is made from Sheep's wool! If you've seen Sheep's wool while it's still on the sheep, it is full of oil, dirt, urine and feces! It takes Chemicals to extract vitamin d3 from Sheep's wool!. Since when has Sheep's wool extract "Lanolin" been on anyone's diet! All we need is a little sun, a little bit of fish and a healthier diet, let's not make this complicated!

from my (admittedly limited) understanding of physics and optics I find it hard to believe that 50 degrees is a magic break point below which NO UVB gets through, and above which MUCH UVB is available. However, I will accept the basic thesis that if the shadow is longer than the flagpole there is very little, and if it is shorter you will gain benefit.

It's possible to be more precise (and this relates to time of day as well as time of year): when your shadow is longer than you are tall, you are not getting any vitamin D. Because of the low angle of the sun, UVB rays are being filtered by the atmosphere.

@hasse_john: You are correct! This is a simplified rule of thumb. The way you really want to measure the UVB radiation is something called "Irradiance", which is an optical measure with units of Power-per-Area (often in units of mW/m^2). We could, more specifically, use another quantity called "Spectral Irradiance" or SI, which only looks at the Irradiance over a small band of wavelengths (in this case, UVB, for example), and SI has units of Power-per-Area-per-wavelength (mW/m^2/nm). (Whew!)

So, geeking aside, ozone 'scatters' UVB light - for the same reason that the sky is blue. So, the more sky it has to go through, the less and less there is. Thus, the atmosphere attenuates (or lessens) the UVB as a function of how much atmosphere it goes through. For example, it's also a rule of thumb that for every 1,000' in elevation, you have an extra ~4% increase of UVB. Here in Boulder, CO, I've got ~22% more UVB than I should just for my altitude. There is some magic threshold of 'enough' UVB that turns on previtamin D production... but I don't know what that *Irradiance* value is. (As a geek, I'd like to know!) ;)

@Reverend Alan: It's true! However, most of the impact of Global Dimming reflects in the visible-to-IR spectrum, and thus doesn't have impact here in the UVB. Still, super-scary we've done that....

@Islander: Climate scientists factor in Global Dimming, along w/ Ozone depletion, and greenhouse gas emissions to determine what's called "Radiative Forcing" of the atmosphere... and that lets them simulate/infer how the climate is changing. They actually do factor against each other!

@JosephDiMasi: thanks for clarifying that. From Wikipedia: "Deliberate manipulation of this dimming effect is now being considered as a geoengineering technique to reduce the impact of global warming." I certainly hope not. That would be an unmitigated disaster!

Regarding showering after sun exposure: You also should not shower before, otherwise you wash away the substance ON (not in) the skin that converts to vitamin D with UVB exposure, according to Chapter 19 of Let's Eat Right to Keep Fit (1954), by Adelle Davis. That showering advice is based on studies by Helmer and Jansen called "The Absorption of Vitamin D Through the Skin" and "Vitamin D Precursors Removed from the Skin by Washing." The date of these studies: 1937!

As an aside: Sunlight consists of an infinite number of wavelenghts, not merely 1500.

I wonder since it's a fact that people have less Breast cancer and Prostate cancer in the sunshine states that's attributed to getting more vitamin D from the sun does this mean they wash less often? The Question was asked by another poster if you wait 48 hours to bathe and go in the sun regularly do you ever bathe?

I firmly believe you can do everything that is ever written about health but if your mental health isn't optimal it won't matter, When i go into a health store of any kind it always strikes me how so many of the people using it don't seem mentality healthy always grasping for the latest health news but the compulsion to be healthy may be in fact an unhealthy obsession, if your not happy you will never be truly healthy and always searching for the latest health news may be in it's self an unhealthy way to live. The saying everything in Moderation often seems to get lost on this or any "health" forum.

Hi watershed... This is a very valid point, and one, that I believe, should be reiterated again from time to time. There is a plethora of very good information -- much of it cutting-edge -- on this site. It comes both from Dr. M (and kudos to him) and from posters (kudos to you), many of whom have vast amounts of experience and information in the nutrition and health field.

As new information becomes known or expanded upon, or as contradictory research uncovers a completely different perspective, the human mind can get confused, discouraged, and even obssessed -- always looking for and seeking a definitive answer. Just when the mind is comfortable with what it considers the Truth, now along comes someone to refine it a bit further, or even to say that it was all wrong. Now, I am not saying for anyone to stop seeking or sharing new information. That is one of the reasons why I love this website! I'm just saying that it can breed a certain compulsion within the mind. And that compulsion, that obssession, and yes, even that form of addiction, can be as detrimental a part of the toxic burden as any deficiency in Vitamin D3.

Be flexible, be a medical detective to see what's right for your own health, and trust your process. Don't feel a victim to anyone or anything. Again, I'm not saying not to make changes, both in the inner and outer worlds. Let everything be the classroom in which you learn and you expand.

I want to say to any pregnant ladies out there now...I read an article that getting your VIT D while pregnant is especially important for the absorption for the fetus & helps with the growing of healthy bones. I also read that if you expose your abdomen while sunning, even in your backyard, it is beneficial, and studies have shown that your unborn child while in utero can distinguish difference between with bright sunlight & times out of the sun. Amazing & so good for those bones forming which need the VIT D. Google it!

Dr. Dietrich Klinghardt has also mentioned that raising your D3 levels, both before and during pregnancy, will significantly lower the possibility of birthing a child who develops symptoms along the autistic spectrum.

I would like to introduce another point of view in regard to the statement that one needs a sun angle of 50 degrees to get UV B. According to the naval calculator, on March 26 my max elevation is 46 degrees, not enough to get good UV B. However, going to the Norway solar vit D calculator at nadir.nilu.no/.../VitD_quartMEDandMED_v2.html which has been referenced in other articles, I find that at my coordinates I receive 1000 units of vit D in 4 minutes. This was calculated for full body exposure. So from this I can only conclude one of two things. Either the Norway calculator is off, or the 50 degree rule is not quite right. Any input would be helpful.

Dr. Mercola stated in the video that the US Naval Observatory table takes Daylight Saving Time into account. It clearly states on the table "The altitude and azimuth values are tabulated as a function of the standard time (daylight time is not used)" Perhaps that error accounts for the difference between the US and Norwegian calculators?

No that would have nothing to do with the discrepancy I described. Daylight saving time would only shift the maximum angle by an hour. In this instance, the maximum was at 12:30 and 12:40 at 46 degrees. Earlier and later times of course are less. The main point remains. The Norway calculator says one can obtain 1000 units of vit D in 4 minutes. Dr Mercola says that no vit D is produced when the max solar angle is less than 50 degrees. We need to have a reference on that.

For those discussing injectable and large doses of vitamin D: There is an important distinction. Elderly nursing home residents and patients on hospitals receive: Ergocalciferol (vit D2, which is not the vit D Dr Mercola refers to in his Vit D information). Cholecalfiferol, D3, is the effective supplement if adequate and proper sunlight can not be received. So if someone you know is in a nursing home, is RX'd vitamin D or in a nursing home, he/she is likely receiving Ergocalciferol, sadly.

@ Heather Marsh, sunshine is free, the only way to make money out of anything which comes free in nature is to make products which are anti that, or which adulterate it. There is no money to be made sitting nursing home residents out in the sun, therefore doing that has to be vilified, the residents kept indoors and then treated for conditions related to insufficient sun exposure with manufactured pharmaceuticals which make someone a lot of profit! *That* then becomes the new good to replace the bad old sun! Happens, as I say, with anything that is our birthright! In the end it is taken away from us and replaced with something which makes someone else rich. Of course, I don't have to tell you that, personally, I realise, but it is so very remarkable, and truly absorbing the implications of that mechanism in our civilisation shifts debates like the one in this thread from a focus on *consumption* (either of natural sunshine or pills or apparatus, etc) to a focus on taking back our birthrights, the result of doing which would be revolutionary!

I have an old family photo taken in 1947 of a baby a few months old lying naked on a rug in the sunshine with its mother beside it whose breasts under her blouse were newly endowed jugs of nutrition. The vivacity and joy of the well-nourished baby's expression and gestures shine out of this photo and say it all, and I'm sure the adult that baby became enjoyed the health boost it received at that time in its life. Now we have "happy" babies in advertisements for soy infant formula, and for drugs against the new childhood diseases of autism, ADHD, and so on and so forth - all of which have to be bought, all of which make some scammer rich, and have replaced the free birthrights of sun and breast!

Great info and advice from Dr. Mercola. A reminder that might be worth mentioning here is that many new readers of this column have no idea just how much chlorine they are absorbing through their skin when they shower (or use a pool, jacuzzi,etc.) Unfiltered showers are especially troublesome in that the steam also contains high levels of chlorine that is breathed in. This is accumulative and needs to be addressed with a good detox program. If not the chlorine will create a tremendous immune system burden over time. Our immune systems have enough issues to deal with on a regular basis. On a microscopic level we can envision our immune system like soldiers on a battlefield since the day we were born. The chlorine might be represented as a group of villans on the attack. We can address this hopefully sooner than later, but we must remain strong and vigilant for other invaders and enemy armies.

---In the past I have heard health advisor/expert Gary Null mention that he adds Vitamin C to a drink before and after sun exposure and that it protects him from burning. I have tried this and it works well for me and I used to burn easily!! I usually consume 1000 mg of buffered vitamin C along with another 500 mg of ascorbyl palmatate vitamin C. Ascorbyl palmatate is fat soluable and tends to remain active in the body much longer than other forms of the vitamin. If I'm out working or playing for approx. two or more hours I add another 1000 mg of buffered C at the end of my sun exposure. I now will definately remember to add astaxanthin, another anti oxidant superstar, as Dr. Mercola suggests.

---My research on damage already done by sun overexposure- It causes our bodies to permanently produce some damaged skin cells which will be removed by a healthy immune system. The worse the damage the more immune soldiers have to be tied up in the battle. Battle loss= SKIN CANCER>>>>>>>>IMPORTANT FOOD TYPES TO AVOID- #1-Hydrogenated and partially hydrogenated oils. #2- GMOs

@dover, there are experts on this board with much more up-to-date knowledge, but I can tell you that I have personally used topical vitamin E (the oil directly out of the vitamin capsule) on burn scars and they have healed beautifully. Several applications a week for several weeks were necessary to achieve this. As well, organic sulfur or MSM crystals are wonderful for regenerating healthy tissue throughout the body. I have only taken sulfur orally. It should be helpful applied topically as well. MSM skin cream is commercially available; but, because commercial creams can contain toxic ingredients, you might be better off making your own at home.

This post was deleted because it violated our Terms Of Use : Abuse, harass, humiliate, deceive, threaten, impersonate, intimidate or engage in any other abusive behaviors with those who comment on Mercola.com.

To add to this article there is also another known reaction of the sun when it stimulates melanocyte stimulating hormone (MSH). Not only does this effect melanocytes in the skin to produce pigment for tanning it also stimulates receptors in the gut to enhance gut health. It will even reduce inflammation in the guts of celiac patients or any other type of inflammatory bowel disease which will aid in the absorbtion of K2 and other synergystic nutrients of vit D.

To verify this you can check this link. www.ncbi.nlm.nih.gov/.../12584408 As you can see there are so many things the sun can do that while producing D3 perhaps countless other things are being produced that will have interaction with D3 and allow for a much more balanced use. Another advantage of sun over oral D3 is preventing overdosing as your body has the infinite wisdom to know what it needs with built in mechanisms to STOP Vitamin D production from sun stimulation or safe tanning bed no matter how much longer you stay in the sun. (I find it interesting that my post was the lead post with many thumbs up and then mysterously got knocked down with out any rebuttal. it's such a positive post, isn't it?)

@extremehands1 - I agree it's possible the body has some mechanism to avoid over-production of Vitamin D3. On the other hand, it seems Summer and Sunshine may be limited by seasons, and seasons of the year may be the natural mechanism of D3 limitation. Regardless of limitations, Sunshine has magic, and even the gloomiest thoughts fade away to be replaced by a sense of Good Cheer.

Balances may be lost by continuously high D3 365 days per year. High D3 throughout the Summer probably serves to Knock Out cancerous growth, and that alone seems a serious health benefit. Islander insisted she failed to find evidence of health disruption due to excessive D3. I would caution that the cancer-fighting property of D3 is something new, and this property probably follows the natural order of seasons to avoid balance-disruptive excess. At the moment, we don't have adequate evidence to say for sure.

Hi enjonn, There are quite a few places you can find reference of the Solar derived D3 shut off mechanism. Dr. Mercola has mentioned this as well. I totally agree with your statements about "balance-disruptive excess" You should see my other post up at the top.

One exception, Enjonn: elderly patients in an assisted living center who were given an entire year's dose of D3 in one injection did not tolerate it well. (That kind of therapy seems patently absurd to me. What were they thinking?) However, the adverse effects wore off quickly and no lasting damage was done. There may be other examples, but none that I recall seeing.

"" were given an entire year's dose of D3 in one injection "" Ouch, who would think up such a thing? And I have to wonder about our prisoners who are not given any direct sunlight while incarcerated and those in solitary confinement for months at a time, even years maybe. Are they trying to destroy their health on purpose?

Love this link @extremehands1! Yes, just like we now appreciate the symphony of whole food nutrition (vs. isolated nutrients) I suspect in time we'll see the benefit of "whole sunlight spectrum nutrition" (vs. isolated wavelengths). Photorepair happens in violet/UVA, collagen production @ 630nm (red), all *sorts* of things in the NIR... the list goes on. We're not plants, but our body certainly knows how to pull energy from the sun!

@Islander - What were they thinking? The article mentioned that this was a study to determine benefits of mega dosing, if any. I don't advocate one gargantuan lump of D3 per year. It seems more natural to distribute D3 in relatively large doses between 8,000 to 20,000 units several days per week throughout a Summer.

Those of us who recently discovered the cancer-fighting power of D3 might prefer a moderate dose daily 365 days per year. But then again, D3 might be considered a Summer and Sunshine benefit, and the seasonal nature of D3 warrants heavy dosages within the season and cessation out of season.

Dr Mercola: "it is my STRONG recommendation to avoid soap on most of your skin". Yes indeed. Soap as it is used now was developed for removing coal dust on miners. If you are not a miner covered in coal dust why soap yourself? It is antagonistic to all the health mechanisms of the skin, and creates a pathological imbalance of skin microorganisms. Like most hygiene and grooming aids soap is anti-health and most such aids exist as a way for you to donate your money to someone and make them rich. These products are no different in that regard to the pharmaceuticals that Dr Mercola rightly battles indefatigably against!

A hot shower was a wonderful pleasure that I enjoyed once a day, but as I have become busier, I might shower once a week. We often have water conservation concerns here in California, and once-a-week seems acceptable. I worry about washing off protective body oils, and I rarely use soap.

I don't know about miners and soap....that might be right....I do know that soap dries my skin and consequently only use it where the sun doesn't shine....Dr. M has brought this point about not washing your skin for 48 hours up before so the processes of making VitD can run their full course....I have research that indicates that swimming in a chlorinated pool will also diminish the skin's work....

It's true about California and water conservation concern's. As we remodled each bathroom we ran the drain on the bathtub outside so they could water fruit trees, lawns and other plants. We even installed an outdoor shower which is more like a rinse off station, up on our deck and the drain water goes into the garden. I can get really dirty working in the garden, moving wheel barrels full of steer manuer etc. and a quick rinse off in the warm sun is a welcome and refreshing break. I often do so 3 times a day.

We do not have any soap or shampoo or cleaners in the outdoors shower. I do not feel I am wasting water if I shower in it before I water the garden with it. All the hot water is heated with solar water heaters. I only feel the need to use soap and shapmoo maybe once a week. In northern California where I live we get all our rain in the late fall, winter and early spring, the other half of the year might not see a sprinkle, after the fog burns off it is full sun all day.

I get in the shower every night but only use unscented olive oil soap on the private parts and under arms. I try to teach my kids to do the same but they are in love with the "smelly" stuff. Most of that stuff smells horrible to me and I get real tired of smelling Dial soap on my hubby after he showers. I much prefer his natural scent.

I make my own shampoo, tooth powder, lotion, chapstick and I have some castile soap that I want to make soap bars from. I get all my products from mountainroseherbs.com. I even made my own hair spray from lemons, water and essential oil, however, I am having a hard time finding the right spray container. The products from Mountain Rose Herbs are either wild harvested or organic.

I have been a long time user and customer of your website but this article has caused me to wonder if I have wasted my time and whether your advice was counterproductive to my health. In your previous articles you said to avoid sunscreens because they block the production of vitamin D and in fact the sun does not cause melanoma. (I stopped using sunscreen years ago based on your recommendations). Now you're saying the sun causes cancer and going out in the periods of the day or year where there is no chance of getting UVB rays is not recommended. The waiting 48 hours before showering is also new. You've got to be kidding - who's going to do that. What's next, Krill oil causes herpes or probiotics is a waste of money?

This is not new information as a simple search on our site will reveal that for many years Dr. Mercola has stated both that UVA rays increase your risk of cancer as well as recommending waiting 48 hours to shower for vitamin D3 to be absorbed into your bloodstream.

"The key point to understand is that sunlight is composed of about 1500 wavelengths, but the only wavelength that will have your body make vitamin D are UVB-rays when they shine on UNexposed skin." Is this a typo? On another note, after probably ten years of asking for D3 levels to be included in my annual blood tests, my GP is finally showing some interest in my levels! Slightly different measurements are used in Australia - he thought my levels were good at 58, but my neurologist feels that with MS 100 is a better level - so she has prescribed a 3 monthly dose of 250,000IU.

yes, here in Christchurch, New Zealand the goal for neurologists for their MS patients is to get levels of 125 which equates to about 40 in the US units. Heather, I guess you're familiar with Dr Terry Wahls' experience and research with MS. I have ordered her book "Minding your Mitochondria" from the public library. They have it on order and I'm number 3 in the queue!

Hi honorarenwick, I watched the You Tube clip and was intrigued. I worked out that I could probably down the raw leafy greens in smoothies (eating them unblended gives me acute gastric distress) and the rest of it - the three cups of cruciferous greens, the 3 cups of colourful fruit and vegetables, the organ meats etc is pretty close to how I ate before I married, so is do-able. Husband insists/prefers that his food be refined and tends to quietly scrape his veges out for the birds :( I just have to find a way to budget my energy account and my food shopping to manage both.

Question for Mercola: Lifeguards spend lots of time outside, but my guess is that they probably take showers afterward. If their D levels are so high then they must be absorbing some of the vitamin D before they shower, likely in the hours that they spend outside. Is there any information about how much D you absorbed if you HAVE to shower after being in the sun?

Showering with water is not the problem, only when you add soap. Remember, as Dr. Mercola has stated many times in the past, it is not necessary to use soap unless you are washing your armpits or groin. Minimal vitamin D is produced in those areas.

#1 sun mistake is to go sunning with deodorant on that contains triclosan, and to avoid a chlorine pool on a sunny day while having deodorant applied. Triclosan combines with chlorinated water to form chloroforms, and triclosan is converted to dioxins in the presence of chlorinted water and UV radiation. Many skin and breast cancers are probably caused through this pathway.

I disagree that UVA is the villian. It's the most abundant UV that we are exposed to. I believe more studies will come out about the benefits of sensible UVA exposure such as news.brown.edu/.../melanin

This is another fantastic article from Dr. M....as I have learned from the continued onslaught of positive articles about this wonder hormone (yes, it's not actually a vitamin but a steroid hormone) adequate VitD levels may be the single most important factor in human health.... I am fortunate to live in Central Texas where we can get these life giving rays year round...too cold days always pass quickly and there is an abundance of sunshine...

I gave up sunscreens years ago, even before the good doctor suggested to...blocking the sun's rays is a huge hoax...now I only use a blend of organic raw coconut oil and organic raw cacao butter...I've learned not to put anything on my body that I can't eat since the skin is the body's largest organ...

i have always been an advocate of Dr. Mercola's info based on sound research. However, my question is, "if you sunbathe every other day, will you never bathe again "? Also, it would seem that before this research about 48 hour absorption came available, everyone bathed, so nobody absorbed vitamin D?

Tony, Thank you for your response to clarify my comments. My only point in making an extreme statement is that we all must be missing something in this entire Vit D process. As humans we tend to overthink and overanalize all that exists in natural form. Afer all, exposing most of the body to sun, historically, has only been going on for a realatively short period of time ( mid 1900s).

wilnervet, when you say "historically" you qualify your statement to the period of time during which records were kept. In fact, we have been exposing most of our body to sun for about 3 1/2 million years. I'm inclined to think that "historically" includes the period during which we started covering up...especially as we migrated into the northern temperate and Arctic zones.

For the purpose of discussion only it is important to realize a that Dr. Mercola made an amazing point when he revealed that there is no UVB radiation coming to earth for a significant period of the year. Can we ignore Mother Nature’s design? All life forms through out our entire evolution have experienced this UVB break since the beginning of time except at the equator. Perhaps there is a reason for this break and it is needed to recalibrate some things. Should we be so anal about getting our winter dose of Sun derived D3 and oral D3. It is also worth noting that there is no amount of vitamin D3 found in natural food that delivers the dose of D3 of the sun in 20 minutes at high noon.

There is only nominal amount of D3 found in natural whole form food. Is there a reason for this? What is Mother Nature telling us here? This post is NOT advice but merely for discussion. Since the body has the ability to stop solar vitamin D3 activation when the amount it needs is reached then we must consider that the correct levels are of critical importance. When the body stops production during sun exposure it preventing over dose to maintain a critical balance in harmony with perhaps countless other factors that are also being produced by the sun. These are all things to consider and needs further study before we indulge in the hype of Oral vitamin d.

You have absolutely no way of determining consciously the exact level of vitamin d you need for your health at a given moment or period of time. The body can down or up regulate nutrients when it needs to create balance in the system. People levels will vary tremendously in the reference range despite similar UVB exposure. These are all things to consider and needs further study before we indulge in the hype of Oral vitamin D3. This post is NOT advice but merely for discussion.

@extremehands1 - Yes, you are right. Even the best of natural foods don't provide whopping amounts of D3, but what about D3 from Sunshine? Dr Mercola has expressed possiblity that a man gains as much as 20,000 units from the Sun on a good day around noon. Your join date is 12/2007, and by now you might have had enough of D3? The rest of us are new to D3, and we are fascinated by this amazing hormone. Major surprise to my mind is the notion that D3 originates from Sebum.

Excatly Enjon! Thanks for your insight. We were meant to get large doses from the sun by which has your internal innate wisdom to guide it's exact amount of production during the period of the year that has UVB availability. There are some authors that have stated that even though it is produced by the sun at high amounts in order to maintain proper levels it will be destroyed or made unusable by the body and is discarded not stored even though fat soluble. I too am excited about D3 in the sebum....then perhaps you can transfer it to someone during intense sweating while making love. Friction certainly heats up the sebum to make it more fluid.

What Dr. Mercola did not mention but was strongly implied, is that man evolved from tropical and sub-tropical areas where the UVB was available nearly all year round. It is only when people migrated further away from the equator that their access to solar vitamin D dramatically decreased. Just because you can’t obtain UVB from where you currently live, it has nothing to do with your genetic design for vitamin D.

Tony R, Thank you for your intuitive thoughts. I did mention "except at the equator." I still have to consider the time of evolution spent away from the equator and even near the equator there were breaks from Solar derived Vit D. This may have contributed to certain genetic changes that allow us to deal with out the D3 for periods of time. I believe lack of sun exposure has everything to do with genetic changes/design as seen in people that genetically have lighter skin in order to be able to absorb more UVB in where it goegraphicly is less. Melanin the skin pigment produced by the sun blocks some UVB.

@Kiloba and all, Lets not forget at one time we were covered in hair and thus minimal UV absorption unless we had fiber optic hair. perhaps loosing our hair aided in rapid genetic changes due to sun exposure. Think of how many animals have hair and their reduced ability to solar derived Vit D. They seem to remain healthy. I think the polar bear has fiber optic hair so maybe they get plenty of it but then again look at their sun angle due to geographic location..

Koliba, thanks for that awesome info. This is reason that I raise fundamental questions when I make posts of simple logic. Although it is controversial I realize it will generate many comments and it is scholars like you that will come forward with great info for people to learn from. I have no problem getting a flury of thumbs down if it means it will generate a balance of comments from both ends.

It will certainly help buffer the extreme views that some may have. That being said....These fur and feather covered animals are producing oil in the skin with D included. Where is the D coming from if not from the sun stimulation through the fur/feathers? I found the answer with in another thread. "In sheep, their fur produces lanolin which turns to D in the UV light, and then they lick it to ingest it." Posted by "JosephDiMasi"

Good on you extremehands1 to raise an important discussion. Think of all the mammals that are inhabiting areas of the globe, where no vitamin production is available for at least ten months in a year (like where I live outside Stockholm in Sweden) according to the notion that the sun needs to be at a position of at least 50° altitude. These furry mammals will not get any vitamin D for most part of the year, and it doesn't matter if they are predators and eat other smaller furry mammals, since they will also have absent vitamin D production most part of the year. And how do the cetacea (whales) fare? UVB don't penetrate very far into the water I guess? And how about fish, do they need vitamin D, and how in that case do they obtain it?

This all sounds quite complicated and I had no idea about being able to wash Vitamin D off! Very valuable information though! I live in the South of the UK and do not wear any sun cream, but usually spend a lot of time out in the sun. I can't afford coconut oil and/or expensive non SPF sun creams, or astaxanthin. But I'm hoping that by eating lots of Lycopene and Kale, I will at least have enough antioxidants to protect me against skin cancer!

@sal1974, Perhaps you may know this but for all...In tomatoes you have lots of lycopene. lycopene helps fight collagenases. Collagenases are basically enzymes that destroy the collagen in your body. Collagen keeps your skin elastic. Lycopene may help prevent saggy skin from sun exposure, especially on the face like Dr. Mercola said. It is also very impotant to note that while excessive sun exposure past the needed amounts may make your skin sag it ALSO may destroy the vtimin D3 in your skin. Vitamin D can be destroyed by over-treatment with ultraviolet (UV) light and by peroxidation in the presence of rancidifying polyunsaturated fatty acids.

How does this relate to the Bates method protocol for restoring natural vision? Does this mean that Bates Method sunning outdoors in the winter is harmful, and that Bates method sunning through windows in the winter is also harmful? Is this why "sunning" with lightbulbs is practiced?

I skimmed through the comments using a search for "UVA" and didn't see anything about a question I have. Since UVB is the vitamin D maker and UVA can even counteract the Vit D formation, why does a "safe tanning bed" only have 10% UVB. Wouldn't it be more effective for Vitamin D to have lamps with less UVA or filter out the UVA? (For someone just wanting a tan, UVA is important)

Sunlight is 95% UVA thus most safe tanning units are designed to closely mimic this percentage. Although there are beds available that produce 100% UVB and 0% UVA, they are not as popular as most people prefer the cosmetic appeal of a tan.

Dear Dr. Mercola; I like the idea of using the USNO calculator for determining the exposure to UVB rays and will accept your use of 50 degrees as the cutoff, BUT I live in a narrow, at least lower populated part of the country that MUST have an adjustment factor. You see I live in the Denver, CO area (my house is at 5,890 ft above MSL) and altitude makes a hugh difference in the sun's effectiveness. The table tops out around 38 degrees for today Oct 31, but I know that a person can still get burned on a sunny day today (red from UVB).

Is there a simple adjustment factor that could be used? Something like X degrees adjustment for every 1,000 feet above Sea Level or some other altitude. If there is then please let me know by return email or publish an update. Thanks for your help and other information. Your articles on sustainable farming vs corporate farming and ranching are very informative. I used to be a Monsanto investor, but have divested and am now a serious detractor. Thanks for waking me up.

Now this is scary.. Recently fibroids are linked to deficiency of vitamin D. Doctors advise the women between the age of 30to 50to take ample sunlight. Reading this article , I feel Fibroids is better than cancer.

True Solar Time vs Zone Time (official time): When using the Sun or Moon Altitude/Azimuth Table mentioned in the above article, not only would you have to adjust for daylight savings time, but also for the difference between zone time and True Solar Time (Sundial Time), which can be significant in some locations. Obviously, the sun doesn't care for our arbitrary time zones ...

This is a useful article, although I could not find a reference supporting the statement that significant uvb rays can be obtained only by being positioned where the sun is at a relative angle of more than 50 degrees from the horizon. Also, since uvb rays, while beneficial in that it brings about the production of vitamin b, can also be harmful, is there a limit to the angle of exposure to the sun, where beyond that angle it becomes harmful and needs to be avoided? I ask because I notice that in my calculations, I see that noon time is always beneficial, which is contrary to what we've always been told. If you're living near or along the equator, where the angle approaches 90 degrees at noon, would sun exposure be still worth the vitamin d benefits because uvb ray exposure can be too strong and thus harmful?

I purchased the Dr Mercola SunSplash REFRESH Tanning Bed and it just arrived today. Looking at the user manual I have found that I have 'normal' skin and have looked at the chart for my times. However, when I read the 'Benefits of Sunlight free Ebook' it says the magic number is 20 minutes. Anyone know which is correct? Does the total time INCLUDE both front and back exposure? I have a stand up bed so should I do 7 minutes PER SIDE or 7 minutes TOTAL? Regards,

Dr. Mercola, in his article titled "Little Sunshine Mistakes that Can Give You Cancer Instead of Vitamin D" contains important advice for light pigmented, not dark-skinned people. Dr. Mercola alludes to this in the statement "If you are deeply pigmented and your immediate ancestors are from Africa, India or the Middle East, it is possible you may not even have to worry about the timing of your exposure."

Blacks need to be aware that many vitamin D articles and vitamin D books do not have information that can be used as guide for dark-skinned people. To the detriment of blacks, many authors do not point this out to readers. Many dark-skinned people therefore think that sun exposure will cause them to get skin cancer and that 10 - 20 minutes of sun exposure per day, will suffice for the dark skinned people.

This one-size-fits all recommendation is very misleading and may have very negative effects on the health of blacks. The high melanin content of deeply pigmented skin serves as a natural sunblock, helping to protect the skin from skin cancer, while at the same time reducing vitamin D production. Blacks therefore need to spend much more time in the sun or take vitamin D supplements to reach a healthy vitamin D level of 70 – 100ng/ml. The book "Correcting The Vitamin D Deficiency Epidemic: Strategies to Fight Diseases and Prolong Life for Black People" contains specific health information for dark-skinned people and was written to fill the void of information for blacks.

Dark pigmented people can expose their skin to far more UV because they are naturally protected from UV damage and given the same exposure as light skinned people, they will have far less skin cancer risk. On the other hand, dark pigmented skin produces less Vitamin D and therefore supplementation is fairly necessary. If you are dark skinned and you work mostly indoors, then you must supplement.

I must say that the information about topical creation of vitamin D on the skin and its assimilation into the body is new to me (I saw it first time in one of you other posts). It is also quite repelling! Most people smell enough bad without having to give them another reason not to wash themselves.

But this is maybe the reason why I, in spite of regular tanning outdoors (when I have the opportunity) and in solarium (most of the year) never manage to move my vitamin D level above 75 ng/ml. Still, I will continue taking showers twice a day but from now maybe save a little bit on the soap.

The 2012 American Academy of Dermatology conference was recently held in San Diego and the tone of article shows the conservative nature of their stance on vitamin D, entitled "Sun Exposure Not Enough to Correct Vitamin D Deficiency" www.medscape.com/.../760456 (must do a free login to view).

I'm looking forward to continued research to validate the many opinions floating out there. In the meantime, I will be testing more sun exposure during the right times this summer for myself to see if I can increase my current vitamin D level from 30 ng/mL.

Dr. Mercola said in the video that the altitude/azimuth table adjusts for daylight savings. It is true that the sun and moon table computes daylight time, but the altitude table does NOT. "The altitude and azimuth values are tabulated as a function of the standard time (daylight time is not used) of the place requested on a 24-hour clock." I greatly appreciate the detailed information, but I wanted to correct that one error. Thanks!

lots of valuable info. Another lie by mainstream "stay out of noon sun", now they found the opposite is true. The glass, i was led to believe if keep my car widow rolled up, i will be protected from sun. Now it turns out the opposite is true. Just a little bit about washing with soap, yes armpits and groin are fine, but don't forget to soap your stinky feet !!! there is very little skin area on feet, not enough to affect the overall absorbtion of vit D

You make it sound way more confusing that it is! The table I'm looking at doesn't ask for all that. Let's try it step by step. First, open a new window or tab with this url: aa.usno.navy.mil/.../AltAz.php

Click on Sun

Make sure that year and day are today (unless you want some future date)

Enter your state and town

Click Compute table

And there you are. I think you can ignore Azimuth and simply note when the sun (in the Altitude column) will be above 50º. Below 50, you'll get little UV benefit as the sun just isn't high enough yet. Of course you want to look at 12 noon or thereabouts (leftmost column)...but you may want to re-compute using a future date to find when the sun will be at the right height in your location.

The article states without reference that "UVA is one of the primary culprits behind skin cancer, and it increases photo aging of your skin." But according to this study www.nature.com/.../nature00766.html 92% of all malignant melanoma had no association with UV-light mutation at all. This article also cites UVB radiation being the type of UV light involved in other types of melanoma, not UVA.

@GunnarLoJarl: The 92% number is in relation to the number of BRAF mutations in melanoma. "The highest frequency of BRAF mutations is in malignant melanoma (Table 1). This does not seem to be related to the effects of ultraviolet light, the only known environmental risk factor for this disease." This statement is misleading and confusing. It is accurate to say that melanoma is unrelated to UV light; it appears in people who are not typically exposed to sun, and melanomas appear in body parts not generally exposed to UV rays. This is well known. What is unsupported and contradicts everything I've read about melanoma is the second half of the statement. Two risk factors have been hypothesized: sunburn and genetics. Note, there are merely suppositions. No one knows with certainty what causes melanoma.

I'm not sure what you mean by "other types of melanoma." The "melanogenesis in response to UVB radiation" is the only reference to UVB, and the footnoted article can't be accessed without a fee. Generally, basal call and squamous cell carcinomas are both thought to be the result of sunburn to frequently exposed areas like the nose, forehead, and backs of hands. In other words, it is sun damage that is postulated to be the cause of non-melanoma skin cancer.

In today's opening article by Dr.M, he warns of the danger of trying to suntan behind window glass. That and a lot of these posts got me thinking about a solar energy class I took 2 years ago. One of the important things that was mentioned in class was the need to use low iron glass. With all that in mind I quickly (due to time constraints) googled "low iron glass". Sure enough, I was able to ascertain that low iron glass has a low degree of reflectivity and a high(er) degree of transparency. Since green houses and solar collectors have become so popular these days, anyone wanting to build a solarium, green house(for their own organic veggies), etc., and be able to suntan indoors safely, this MIGHT be helpful. Unfortunately, modifying most existing vertical windows with low iron glass would probably not overcome the 10am-2pm limitation.

Yes, because the link posted here goes to the main/home page (aa.usno.navy.mil/.../RS_OneDay.php )... You only see the "compute table" nice itsy-bitsy (first at left) button in the page "Sun or Moon Altitude/Azimuth Table", which you reach through the left bar site's navigation, choosing "Data Services" then subsequently clicking in "Altitude & Azimuth of Sun or Moon" or easier... here is the site page link, right away => aa.usno.navy.mil/.../AltAz.php

I guess Dr. Mercola mentioned the table's name a couple of times in the video also, check out! I usually check Mercola's news in the morning and sometimes half asleep hence the attention curve being also dormant... ;-) Cheers!

My question is: How does this advise apply to people who live in New Zealand where the ozone layer has holes. The sun in NZ is so bright and very intense. I was there at Christmas and on the days when the sun did shine it was too hot and intense for me.

Yes,I'm from NZ too and was wondering the same thing. We are told that anyone south of Blenheim will be Vit D deficient at some time of the year and 50% of us are Vit D deficient all year round (including me). My levels are about 13 on the US scale so I'm taking 8,000 i.u. a day (1.25mg weekly)of Vit D3 and will have my levels tested in May. I work with dermatologists here so will ask one if they have any data on how the ozone layer depletion affects us.

I understand that the ozone hole was actually never directly above us but in a lower latitude over the Antartic, that it has shrunk and is also only present in Spring. Apparently due to the asymmetric elliptical orbit of the sun, the Southern Hemisphere is actually closer to the sun during its summer than the Northern Hemisphere is during its summer months. However I see there are quite a few professionally knowledgable contributers here so I'm open to being corrected...cheers,

What about those of us who can only get out in the sun on weekends? What should we do the rest of the week for our Vitamin D3? Supplement like we do during the winter? Or reduce the amount of supplementation in the summer? It would be nice to get out in the sun every day! But having a day job makes it impossible. This explains why we get more colds and flu in the winter. Since I started taking a Vitamin D supplement, I have far fewer sinus infections than I used to!

If getting into the sun is a challenge or if you are in a winter climate an alternative option would be a safe tanning bed (electronic ballasts not magnetic). If that is also not an option, oral vitamin D supplementation is recommended.

Replying to Dover--- See Kolibakoliba's comments above for help in repair from sun damage. Cumin also known as circumin can be consumed in many forms. It's regularly added to asian foods and is especially favored in Indian dishes. I find it quick and convenient to take circumin (turmeric) supplements. It is highly rated as an anti carcenogen. Aloe vera gel is soothing when applied to sunburned skin and is also recommended as a drink. It can be found at any health food store. Another highly rated immune system food group (or supplement) superstar would be maitake, reishi, and shitake mushrooms. When consumed these mushrooms stimulate and increase immune system natural killer cells (T cells)in the body.

Picture the body's battlefield. Consuming mushroom is just like giving your soldiers added weapons to fight the enemy. Remember the pac-man video game? The T cells go around in the body gobbling up damaged (cancerous) cells before they have a chance to multiply. We want to keep our immune systems as strong and healthy as possible for the continued onslaught. Citrus fruits (vitamin C)and extra virgin coconut oil (monolauric acid) are potent antivirals. Olive leaf extract and oil of oregano are potent anti fungal and antibacterials. Viruses,bacteria and funguses must continually be dealt with by our immune system. The right kinds of foods can help us to not have to fight the battle with one hand tied behind our back!

veritasoreventus... Cumin is NOT the same as curcumin. Cumin is a spice that comes from seeds atop a plant that is somehow related to parsely. Curcumin is from the East Indian spice called turmeric, and is ground from the root. Turmeric is widely used in Indian cooking (as is cumin, but less so) mainly in tropical oils that won't oxidize within the turmeric. It's daily consumption is usually attributed to the relatively low percentages of cancer and neurodegenerative disorders on the Sub-Indian Continent.

Thanks for the headsup ccnaturally! Dr. Mercola's column and followup forum is one of the greatest educational tools that's available on the web today. I can see why people obtain rankings such as your level 3 Superuser rating. You are astute, correct and, as my screen logo implies in latin: it's my turn to pay the consequences for not speaking the truth.

For the same reason that sunscreen is valuable for facial skin, neck and upper chest and backs of hand also benefit, especially in a car where sunlight is filtered through glass which takes out the UVB rays as mentoned in the article). I do spend a few minutes every day without any sunscreen at all, including face, but I put on sunscreen in my car or if I'm going to be outside for quite a while, at least on face, neck and hands, and tops of feet if I'm barefoot or in sandals. These are the thin skinned, damage prone areas, and they get a lot of sun exposure. Just protecting the face isn't quite enough.

I'm curious, if Astaxanthin acts as an internal sunscreen, does it interfere with Vitamin D production in any way? And last, I REALLY appreciate the information on times of day throughout the year to get UVB exposure. I'll definitely start avoiding exposure during the other hours. According to the charts, in my area (southeastern US), mid March to the end of September is the time where there is a benefit. I put the times on my calendar for the beginning and last days and the fifteenth of each month in between. Thank you so much for the info and the links!

I'm confused I get lots of sunshine all year around here at latitude 32o south now it seems I don't get any vit.d as I shower every day tho I am heavily tanned on my arms and legs don't over do it on my back and chest tho. definitely need to shower as we've had 8 heat waves since Nov. up to 42 d

The way I read it was that soap would wash the Vitamin D off the skin so don't use soap for 24 hours after your good sun day. It seems like a water rinse is just fine after a hard days work in the sun. Use water from a deep well if you can find it.

From "The Monosaccharide Man:" EXCELLENT. Thank you. Under what title is Dr. Mercola's explanation of the BAD CHEMICALS used in most Sun Screen products? Additionally, it is a fact that the Best skin care / moisturizer products must contain Stabalized Aloe Vera (Manose), especially after sun exposure.

The link here in the article goes to the main page of The United States Naval Observatory (USNO). The site's page link of that particular table is aa.usno.navy.mil/.../AltAz.php However, you can go from the main page too, look at the left bar navigation on the main page, click on "Data Services" (goes to)=> "Altitude and Azimuth of Sun or Moon" and you get the page of the link I pasted above. Cheers.

There is another site, www.esrl.noaa.gov/.../solcalc, which I find extremely handy. It has some Australian cities in it, but you should be able to enter your Longitude/Latitude data (as I do). Once you have your location, you can enter the date, exact time and get not only the elevation of the sun, but the direction presented graphically on the map. You can have the map zoomed right on your location. You can try different times of the day to see when the elevation goes above/below 50°.

Actually, I made a video more than a year ago that describes one method of calculating the azimuth (height) of the sun wherever and whenever you are. you can find it on Youtube here: www.youtube.com/watch. The exact instruction starts 1 minute and 20 seconds into the video.

O k I hav a couple Big Quests:1)Can You benefit from Sun Relection/reflectors/mirrors, Being close to the reflection on the water/waves to intensify the The Ultraviolet "B"for less time in the sun? 2)Okay, What about My angle of exposure in the off season ie; instead of laying down and having the sun hit at a 45-degree angle,I stand or sit in a chair so the sun hits at a more perfect/Perpendicular to me ? 3)What about Higher elevation ??

It is definitely not about your particular angle as by the time the sunlight reaches you te UVB is either there or it isn’t. It has everything to do with the angle of the sun through the atmosphere, which screens out the UVB if there is rain clouds or if the angle is less than fifty degrees.

(1) Mirrors & Reflectors will take the sun's energy over a larger area and 'concentrate' it on you. Snow and Water do indeed do this, too... although they absorb a little light, and aren't quite as efficient. (Snow is ~80%, I believe, and water is less...) However,there is generally a *lot* more snow or water around you than reflectors/mirrors, so it can definitely add-up! Note, however, if the UVB got stripped-off in the upper atmosphere already, the reflectors/snow/water will only be concentrating the light that made it through (i.e. - mostly visible & UVA).

(2) The angle that Dr. Mercola is talking about is the angle through the sky - specifically the ozone layer. This is important b/c the ozone layer 'scatters' out the UVB if the sun is coming through at too shallow of an angle. Therefore, your body's 'angle' w/ respect to the sun isn't critical regarding UVB percentages. (It will, however, slightly impact your skin's "absorbance" of the light, as reflectivity is a function of angle... but that's a much more complicated subject...) ;)

(3) The ballpark figure is that UVB increases ~4% for every 1,000' in elevation. For example, I live in Colorado ~5,000'. Thus, we would receive ~20% more UVB radiation than Dr. Mercola's method will predict. (Now what I don't understand quite yet is how that relates to the "magic threshold" of 50 degrees elevation... because truthfully, *some* UVB is getting through at, say 47 degrees, right? Just not enough to activate VitD production. Or am I missing something??

JosephDiMasi, Your post is great. It was of interest to me because you will always see people angle the length of their body at perpendicular to the sun. So as you are saying being perpendicular to rays give you more sense of heat from the light from less light being reflected but not more UVB and or UVA compared to more or less angle. So no matter what angle as long as your skin is exposed to the rays it will tan and get Vit D. That's what I'm getting from your post.

@Extremehands: OK... I wasn't quite complete enough about this in my thinking. There's a few things going on regarding your body's angle: If the body is perpendicular to the sun, you'll catch a larger 'footprint' of sunlight. The energy of the sun is distributed over *area*, so spreading out perpendicular will capture the most light. I'd guess that's probably the most important factor in light absorption.

Now, to second-order, the angle of which light hits a surface does affect how much is absorbed vs how much is reflected. This is called the Fresnel Reflections. (en.wikipedia.org/.../Fresnel_reflection ). This is why there's a glare on the water when the sun gets lower, and polarized sunglasses work. Cool stuff.

But, I would *guess* that this doesn't really apply so much to skin - as it's a rough surface, it probably absorbs sunlight pretty much the same at any angle. So, yes, you still get your D. But again, you're not capturing as many sunrays in total.

I would like to know whether it is safe for me to use a sun lamp. I am deficient in Vitamin D which is being supplemented by a monthly ampoule of 100,000 units. I would prefer to do the whole thing naturally with a UVB lamp. My father who had a greatly different attitude to the sun (he used to go out all hours without hat or sunscreen) and a greatly different skin type (he hardly ever burned that I remember) died of a melanoma at the age of 91 and my doctor says there is no point - and some danger - in using a UVB lamp, especially as old skin can't make Vitamin D, and I can have the supplement for the rest of my life. Anybody, any views ?

You certainly could use a UV lamp. One problem with them is that they only cover a very tiny surface area of your body making them highly inconvenient. You would need to use one for hours to generate any vitamin D. Additionally most of the lamps have a mandatory government imposed shut off after a few minutes, followed by a 10 minute delay for the lamp to recover before you can turn it back on again.

One nice thing about D3 supplements is that you won't get melanoma. But serious attempts to obtain high D3 should watch Vitamin K2. High D3 can result in Calcification of soft tissues, and it's good to enjoy fermented foods, such as pickles and other fermented veggies. Cheese comes from fermented milk. Some people complain of constipation from cheese, but cottage cheese might suit those people.

Thanks for the replies. I'll use the sun when I can, and having read all this stuff and Holick's book feel safe to do so. I quite like the idea of not washing obsessively ! As to K2, I'm eating natto every day. I make it myself and its very stringy as good natto is supposed to be. I guess yogurt also helps, as well as natto and cheese.

Also according to the reference "iii UVB Radiation, Colorado State University" provided by Dr Mercola above and e.g. this wikipedia article en.wikipedia.org/.../Ultraviolet , the most biologically harmful UV radiation reaching the surface of the earth is UVB. This makes logical sense, since the shorter the wavelength of the radiation, the more energy it contains and emits when hitting some material like your skin.

So the more I read about this, the more confused I get about the info shared in this article. I simply will have to look more into this matter. UVC has the shortest wavelength and is germicidal (e.g. at wavelength 254 nm), simply because it damages the DNA so replication is stopped. At even shorter UVC wavelength (183 nm) the radiation additionally produces ozone from oxygen, and this technique is used by the air purifiers that mercola.com sells, since ozone is very reactive and will oxidize almost anything it comes into contact with. Fortunately UVC is almost completely blocked in the atmosphere, so it doesn't reach the biosphere. This planet certainly is designed to host biological life! <3

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